Electrophotographic developing apparatus



y 1962 K. J. MAGNUSSON 3,032,009

ELECTROPHOTOGRAPHIC DEVELOPING APPARATUS Filed Dec. 5, 1958 2 Sheets-Sheet 1 INVENTOR. KNUT J. MAENLISS EIN 2 Sheets-Sheet 2 Filed Dec. 5, 1958 INVENTOR. KNUT J. MAENU SSUN BY 3 032,009 ELECTROPHOTORAPHHJ DEVELOPING APPARATUS Knut J. Magnusson, Princeton, NJ assignor to Radio Corporation of America, a corporation of Delaware Filed Dec. 5, 1958, Ser. No. 778,541 11 Claims. (Cl. 118-637) This invention relates generally to developing apparatus for developing electrostatic latent images by an electrophotographic method, and more particularly to apparatus for developing such latent images quickly on a continuously moving web of record material. The developing apparatus of the present invention is particularly useeful for developing latent images exposed on a continuously moving web of record material by means of a flying spot scanner.

Prior art electrophotographic developing equipment for a continuously moving web of record material has been relatively bulky and has occupied considerable space in the direction of travel of the web. Most prior art developing apparatus provided a hopper for the developer mix that was substantially coextensive with the width of the traveling web. The time elapsed between the exposure of the image and the time when the developed picture could be viewed had been relatively long. This type of developing apparatus was, therefore, unsatisfactory for applications where it was desired to develop the image substantially immediately after it had been exposed.

Accordingly, it is an object of the present invention to provide novel and improved electrophotographic developing apparatus that will permit one to view the exposed image relatively quickly on a continuously moving web of record material.

It is another object of the present invention to provide improved electrophotographic developing apparatus that is relatively more compact over the record to be developed so that one can view the developed image almost immediately after it has been exposed.

Still another object of the present invention is to provide improved electrophotographic developing apparatus for a continuously moving web of record material wherein a hopper for the developer mix is disposed to one side of the web, screw means are provided to move the developer mix across the web, and endless belt means are provided to return excess developer mix to the hopper.

In accordance with the present invention, the following objects and related advantages are attained by developing apparatus wherein the hopper for the developer mix of magnetic particles and toner powder is disposed on one side of the moving web of record material. An Archimedean feed screw of magnetic material, having one end within the hopper, extends laterally through a side wall of the hopper. Means are provided to rotate the feed screw within a channel in a manner to move the developer mix from the hopper transversely across the moving web.

A magnetic field is provided to cause the magnetic particles of the developer mix to form a brush with the feed screw. An endless belt of magnetic material collects the developer mix at the far edge of the web and returns it through a conduit to the top of the hopper. The endless belt is disposed in a separate channel adjacent to the feed screw channel and serves to pick up any excess developer mix that may be carried from the feed screw channel to the belt channel by the moving web. A soft iron shunt is arranged in a manner to demagnetize the belt where it enters the hopper so that most of the developer mix carried by the belt drops into the hopper. The amount of the developer mix on the belt, where it leaves the hopper, can be controlled by the size and location of the shunt and the stiffness of a spring that contacts the belt over the hopper.

3,032,009 Patented May 1, 1962 The novel features of the present invention, as well as the invention itself, both as to its organization and methods of operation will be understood in detail when considered in connection with the accompanying drawings in which, similar reference characters represent similar parts, and in which:

FIG. 1 is a schematic drawing of electrophotographic apparatus of the type employing the novel developing apparatus of the present invention;

FIG. 2 is a front elevational view, in perspective and with parts cut away, of the electrophotographic developing apparatus of the present invention;

FIG. 3 is a front elevational view of the electrophotographic developing apparatus, in cross-section and with parts cut away, to show some of the novel features of the invention;

FIG. 4 is a cross-sectional view of the electrophotographic developing apparatus taken along the plane 44 of FIG. 3 and viewed in the direction of the arrows;

FIG. 5 is a cross-sectional view of the hopper of the developing apparatus of the present invention taken along the plane 5-5 of FIG. 3 and viewed in the direction of the arrows; and

FIG. 6 is a cross-sectional view of the developing apparatus taken along the plane 66 of FIG. 3 and viewed in the direction of the arrows.

Referring now to FIG. 1, there is shown apparatus for providing a moving web 10 of record material with latent images, and apparatus, in accordance with the present invention, for developing the latent images while the web 10 is moving continuously. The object (not shown) to be imaged on the web 10 is scanned by a flying spot scanner 12, employing any suitable flying spot scanning technique known in the art. The scanning and video circuits of the flying spot scanner 12 are connected to a cathode ray tube 14 in a manner to produce a repetitive line scan on a face thereof. The flying spot of the line scan is projected onto the web 10 through a mirror 16, an optical system 18, and a mirror 20. It will now be understood that the image to be recorded on the web 10 may be built up by exposing the web 10, line by line, by the flying spot technique.

The web 10 is supplied from a supply roll 22 to a take up roll 24 via a drive roller 26 and idler rollers 28 and 30. The web 10 is fed between the drive roller 26 and a pressure roller 32; and the drive roller 26 is driven by a motor 34. The take up roller 24 is driven by any suitable means (not shown). The web 10 which comprises an upper photoconductive coating has a charge placed upon it by means of upper and lower corona discharge devices 36 and 38. The corona discharge devices 36 and 38 provide the photoconductive layer of the web 10 with a uniform electrostatic charge, by means known in the electrophotographic art. This uniform electrostatic charge is differentially discharged by the flying spot exposure at the exposure station 39 to form an electrostatic latent image, in a manner well known in the electrophotographic art.

As the moving Web 10 leaves the exposure station 39, it moves through the developing apparatus 40 where the latent image is developed. It will now be understood that the web 10 is developed almost immediately by means of the developing unit 40 after it leaves the exposure station 39. A heater 42 is placed beneath the web 10 at a short distance from the developer 40 in order to fuse the developer toner powder onto the web 10.

Referring now to FIGS. 2, 3, 4, 5, and 6, there are shown the novel features in detail of the developing apparatus of the present invention. The developer unit 40 comprises a base 44 having a flat upper surface 46. The base 44 may be made of any non-magnetic material, such as brass. The web 10 is directed over the upper art.

surface 46 of the base 44 along a predetermined path whose direction is indicated by the arrow 48. A hopper 56 extends upwardly from the base 44 and is disposed to one side of the path 48 taken by the web 18. The hopper 56 is adapted to be filled with a developer mix comprising a mixture of a finely divided magnetic material and a toner powder.

Means are provided to transport the developer mix 52 from the hopper 56 transversely across the web 10 to develop the latent image on the web 16. To this end, the hopper 56 is formed with a pair of aligned holes 54 and 56 adjacent the bottom of the hopper 50. An Archimedean feed screw 58 has one end disposed within the hopper 56 and the remaining portion extending through the hole 54 and transversely across the web it). A shaft 60, to which an end of the feed screw 58 is splined, extends into the hopper t) and is adapted to rotate the feed screw 58 by means of gears 61 and 62 and by means of a motor (not shown). It will now be understood that the feed screw 58 will feed the developer mix 52 transversely across the web 16 when the feed screw 58 is rotated.

The feed screw 58 is adapted to rotate within a channel 64 in a nonmagnetic bar 66 disposed over the feed screw 58. The bar 66 is fixed to the hopper 56 by any suitable means (not shown).

Means are provided to return the developer mix that has been transported across the web ll) by the feed screw 58 back to the hopper 56). To this end, an endless belt 68, such as an endless bead chain, has a portion of it disposed substantially parallel to the feed screw 58.

, Means are provided to move the endless belt 68 in the path of a loop in a manner to pick up the developer mix 52 at the end of the feed screw 58 remote from the hopper 56. The belt 68 is driven by a pulley 76 which, in turn, is driven by any suitable motor (not shown). A portion of the belt 68 is made to move within a conduit 74. One open end 76 of the conduit 74 is disposed at a point adjacent the end of the feed screw 58 remote from the hopper 50. The other open end 78 of the conduit 74 communicates with the upper end of the hopper 56. Thus, it will be understood that as the belt 68 is moved, the beads of the belt 68 will engage the developer mix and transport it through the conduit 74 to the hopper 50.

The belt 68 is directed along a path substantially parallel to the feed screw58 by being confined Within a channel 80 in a non-magnetic bar 82. The bar 82 is separated from the bar 66 by a strip of magnetic material 84. The bar 66, the strip 84, and the bar 82 are aligned with each other and fastened together by any suitable means, as by screws 86.

Magnetic means are provided so that a portion of the feed screw 58 and a portion of the endless belt 68 will move in a magnetic field. A relatively wide magnet 88 is fixed beneath the base 44 and aligned with the strip 84. A relatively wide magnet MB is also disposed between the conduit 74 and the upper portion of the strip 84 and aligned therewith. Since the developer mix 52 contains magnetic particles, the magnetic particles will adhere to the feed screw 58 so as to form a brush of magnetic particles that will brush adhering toner powder against the web in order to develop the latent image thereon. The toner powder of the developer --mix has a suitable electrostatic charge, as is well known in the Also, any magnetic particles adhering to the endless belt 68 will also brush against the web 10 and thereby serve to aid in the developing and cleaning up of the web 10. A permanent magnet 92 and a pole shoe 94 are disposed around the conduit 74 to help magnetize the endless belt 68 so that it may more effectively carry the developer mix 52 back to the hopper 56.

A spring 96, fixed to the top of the hopper St) in any suitable manner, is adapted to engage the endless belt 68 over the hopper 56. The tension of the spring exerted A permanent magnet 102 is disposed beneath the pulley compartment 168 and serves to remagnetize the belt 68. The belt 68 may now pick up magnetic particles and act as a clean up brush when it passes over the web 10.

The operation of the developing unit 46 will now be explained. The web Til, with the latent electrostatic image thereon, is fed continuously from the exposure station 39 through the developer apparatus 4%). The developer mix 52 from the hopper St) is moved transversely across the exposed web lit) by means of the Archimedean feed screw 58. The latent image on the web 18 is thus developed by the toner powder of the developer mix. The channel 64 in the bar 66 and the channel 86 in the bar 82 communicate with each other at the end of the feed screw 58 at a point remote from the hopper 5d. The excess developer mix 52 is then carried intothe conduit 74 by means of the endless belt 68.

Since the endless belt 63 travels in the magnetic field provided by the magnets 88 and 9t and also in the magnetic field created by the permanent magnet 92 and the pole shoe 94, the magnetic particles and the excess toner adhering thereto are transported from the point adjacent the remote end of the screw 58 back to the hopper 56. As the endless belt 68 moves across the web it), it picks up any magnetic particles that may have leaked from the channel 64 to the channel 80, due to the movement of the web 16.

By diverting the magnetic field from the permanent magnets 88 and 96 near the hopper 50 by means of the soft iron shunt 98, the developer mix 52 moved by the endless belt 68 falls from the belt 68 into the hopper 50. The spring 96 in contact with the belt 68 also causes excess developer mix to fall into the hopper 56 by a shaking action. Any developer mix 52 lefit on the endless belt 68 is carried into the pulley compartment 108 where it may be picked up again by the belt 68 under the influence of the magnetic field provided by the magnet 102.

The iron particles under the influence of the magnetic field act as a clean up brush when they pass over the web 10, and thus the belt 68 contributes to the development of the web 10.

Toner powder should be added to the hopper 56 because the continuous development of the web 10 depletes the supply. The toner powder can be mixed with the magnetic particles by any means known to the art, as by a mechanized stirring rod, a rotating paddle, or any other well known means.

Thus, there has been shown, in accordance with the objects of the present invention, an improved relatively narrow developer unit that permits the viewing of a developed image on a continuously moving web almost immediately after the exposure. While the screw means of the developer unit has been shown as an Archimedean feed screw, and while the endless belt has been shown as 'a beadchain, it will be. understood that other feed screws and endless .belts may be used within the scope of the instant invention.

What is claimed is:

1. In apparatus of. the type wherein a web of material may be charged with an electrostatic latent image and wherein said web may be moved along a path past a developing station; developing apparatus comprising a hopper for holding a developer comprising a mixture of magnetic particles and a toner powder, screw means of magnetic material disposed over said web and having one end extending into said hopper, means to rotate said screw means in a direction to cause developer to move over said web from said one end to the other end of said screw means, an endless belt of magnetic material having a portion disposed substantially parallel to said screw means and adapted to contact developer adjacent said other end of said screw means, a conduit for said belt communicating with said hopper and with said developer at said other end of said screw means, means to move said belt in a loop to move said developer at said other end of said screw means to said hopper, and magnetic field means disposed adjacent to said conduit to form a brush of said screw means and said magnetic particles and to aid said belt in moving said developer.

2. In apparatus of the type wherein a web of material may be charged with an electrostatic latent image and wherein said web may be moved along a path past a developing station; developing apparatus comprising a hopper for holding a developer comprising a mixture of magnetic particles and a toner powder, screw means of magnetic material disposed over said weband having one end extending into said hopper, means to rotate said screw means in a direction to cause developer to move over said web from said one end to the other end of said screw means, an endless belt of magnetic material having a portion disposed substantially parallel to said screw means, means defining a separate channel for said screw means and for said portion of said belt parallel to said screw means respectively, said separate channels communicating with each other :adjacent said other end of said screw means, a conduit for said belt communicating with said hopper and with said developer at said other end of said sc-rew means, means to move said belt to move said developer at said other end of said screw means to said hopper, and magnetic means disposed adjacent to said screw means and to said conduit to cause said magnetic particles to form brushes with said screw means and said belt.

3. Apparatus for developing images on a record receiving member moving along a predetermined path, said apparatus comprising: a hopper for a finely-divided mixture of a magnetic material and a toner powder; screw means of magnetic material extending outwardly from said hopper and across substantially the full width of said path; means coupled to said screw means to rotate it to move said mixture out of said hopper and across a record receiving member moving along said path; a conduit extending from a point adjacent the outer end of said screw means to said hopper; an endless belt of magnetic material defining a course a portion of which extends across said path adjacent to and substantially paral lel with said screw means and through said conduit, the portion of said course adjacent said screw means being disposed on the side of said screw means which is in the direction of movement of said record receiving member, means for moving said endless belt along said course and means for providing a magnetic field about said screw means and at least about the portion of said conduit adjacent the outer end of said screw means.

4. Apparatus for developing images on a record receiving member moving along a predetermined path, said apparatus comp-rising: a hopper for a mixture of magnetic particles and a toner powder, a feed screw of magnetic material having one end disposed within said hopper, said feed screw extending outwardly from said hopper and across substantially the full width of said path; means coupled to said feed screw to rotate it and move said mixture out of said hopper and across a record receiving member moving along said path; a conduit of non-magnetic material extending from a point adjacent the outer end of said feed screw to the top of said hopper; an endless belt of magnetic material defining a course across said path extending adjacent to and substantially parallel with said screw means and through said conduit; the portion of said course adjacent said feed screw being disposed on the side of said feed screw which is 'course, means for providing a magnetic field about said feed screw and said conduit, and means for weakening said magnetic field about said conduit in the vicinity of said hopper.

5. Apparatus for developing a latent electrostatic image on a web of record material moving past a developing station along a predetermined path; said apparatus comprising: a hopper for a developer mixture of magnetic particles and a toner powder disposed to one side of said path; screw means of magnetic material having one end extending into said hopper, the remainder of said screw means extending across substantially the full Width of said path; means to rotate said screw means to move developer mixture from said hopper and across said Web; a conduit extending from a point adjacent the outer end of said screw means to said hopper; an endless belt of magnetic material defining a course extending across said path adjacent to and substantially parallel with said screw means and through said conduit, the portion of said course adjacent said screw means lying along that side of said screw means which is in the direction of movement of said web; means for moving said endless belt along said course, and means providing a magnetic field around the portion of said screw means extending over said path and around the portion of said endless belt and conduit adjacent said screw means.

6. Apparatus for developing a latent electrostatic image on a web of record material moving past a devel oping station along a predetermined path; said apparatus comprising: a hopper for a developer mixture of magnetic particles and toner powder disposed to one side of said path, screw means of magnetic material having one end extending into said hopper, the remainder of said screw means extending transversely across substantially the full width of said path; means to rotate said screw means to move developer mixture across said web; an endless belt of magnetic material defining a course a portion of which extends across said path adjacent to and substantially parallel with said screw means and on one side thereof which is in the direction of movement of said web; means for moving said endless belt along said course, means defining two parallel channels across substantially the full width of said path for each of said screw means and said endless belt, said channels communicating one with the other adjacent the outer end of said screw means, and a conduit for said endless belt extending from a point where said channels communicate one with the other to said hopper.

7. Apparatus for developing a latent electrostatic image on a web of record material moving past a developer station along a predetermined path; said apparatus comprising: a hopper for a developer mixture of magnetic particles and a toner powder disposed to one side of said path; screw means of magnetic material having one end extending into said hopper, the remainder of said screw means extending transversely across substantially the full width of said path; means to rotate said screw means to move developer mixture from said hopper and across said web; an endless belt of magnetic material defining a course a portion of which extends across said path adjacent to and substantially parallel with said screw means; said portion of said course lying on that side of said screw means which is in the direction of motion of said web; means for moving said endless belt along said course; means defining a separate channel across substantially the full width of said path for each of said screw means and said endless belt; said channels communicating one with the other adjacent the outer end of said screw means; a conduit for said endless belt extending from a point where said channels communicate one with the other to said hopper, and means for providing a magnetic field adjacent said remainder of said screw means and said endless belt in said portion of said course.

8. In apparatus including means for moving an electrophotographically sensitive sheet along a predetermined path, means adjacent said path for uniformly electrostatically charging said sheet and means for exposing said sheet to a light image; the combination therewith of developer apparatus comprising a hopper for a developer mixture of magnetic particles and a toner powder disposed to one side of said path; screw means of magnetic material extending across substantially the full width of said path and having one end extending into said hopper; means for rotating said screw means to move developer mixture from said hopper and across said sheet; an endless belt of magnetic material defining a course a portion of which extends across said path adjacent to and substantially parallel with said screw means, said portion of said course lying on that side of said screw means which is in the direction of movement of said sheet; a conduit surrounding said endless belt from a point adjacent the outer end of said screw means and communicating with said hopper; and, means for moving said endless belt along said portion of said course and through said conduit.

9. In apparatus including means for moving an electrophotographically sensitive sheet along a predetermined path, means for applying a substantially uniform electrostatic charge to said sheet and means for exposing said sheet to a light image; the combination therewith of developer apparatus comprising: a hopper for a developer mixture of magnetic particles and toner particles disposed to one side of said path; screw means of magnetic material extending transversely across substantially the full width of said path and having one end extending into said hopper; means for rotating said screw means to move developer mixture from said hopper and across said sheet; an endless belt of magnetic material defining a course at least a portion of Which extends across said path adjacent to and substantially parallel with said screw means, said portion lying on that side of said screw means which is in the direction of movement of said sheet; a conduit surroundingtsaid endless belt and having one open end adjacent the outer end of said screw means and having another open end communicating with said hopper; means for moving said endless belt along said portion of said course and through said conduit; and, means for providing a magnetic field adjacent said screw means, said portion of said course and at least that portion of said conduit near said one open end.

10. Apparatus for developing latent electrostatic images on a record receiving member moving along a predetermined path, said apparatus comprising; a hopper for a developer mixture of magnetic particles and toner powder; screw means of magnetic material extending outwardly from said hopper and across substantially the full width of said path, said screw means being rotatably mounted to move developer mixture out of said hopper and across a record receiving member moving, along said path; an' endless member of magnetic material defining a course a portion of which extends across said path ad jacent said screw means and on that side thereof which is in the direction of movement of said record receiving member, and meansfor imparting motion to said endless member along said course.

11. The apparatus of claim 10 including a conduit surrounding said endless member for a distance extending from a point adjacent the outer end of said screw means to said hopper.

References Cited in the file of this patent UNITED STATES PATENTS 2,716,048 Young Aug. 23, 1955 2,832,311 Byrne Apr. 29, 1958 2,846,333 Wilson Aug. 5, 1958 2,854,947 Giaimo Oct. 7, 1958 2,857,290 Bolton Oct. 21, 1958 2,887,023 Young May 19, 1959 2,932,278 Sims Apr. 12, 1960 

